1. Field of the Invention
This invention relates to improving performance efficacy of non-aqueous paint and varnish remover compositions containing volatile components, and more particularly, by addition of pre-optimized solvent based compositions. Optimized solvent based compositions consist of mixed polar solvents and an activator. The activator can be either the volatile components or optionally lower boiling ethoxylated esters like ethoxy ethyl propionate (EEP). The pre-optimized compositions are described in application Ser. Nos. 14/885,996, 14/805,33b 2 and 14/830,436, referred to hereinabove.
There are several paint stripping compositions in commercial use containing high amounts of volatile solvents. As used herein, the term “volatile solvent” means a solvent having a boiling point of less than 90° C. at atmospheric pressure or a vapor pressure greater than 70 mm of mercury at 25° C.                Some examples are: Methylene Chloride, Methanol, Ethanol, Isopropanol, Acetone, Methylethyl Ketone, and aliphatic hydrocarbon containing up to six carbon atoms.        
Although known paint stripping compositions containing high levels of volatile components greater than 40% and, in some cases, greater than 70% have cost advantages and are effective in removing paints and varnish, they have certain major disadvantages. These disadvantages include high inhalation toxicity for the users, the presence of suspect carcinogens, high flammability, deficiency of oxygen when used in low ventilated surroundings, and leakage via vapor loss from defective containers. In addition, the use of certain of these volatile compounds, e.g., methylene chloride, is highly regulated by environmental agencies around the world. These compounds also often exhibit redeposition of the removed paint from the substrate during the paint striping process requiring retreatment. This, in turn, requires the need for to use larger amounts of the volatile paint stripping compositions measured by weight of the formulation/unit area of the treated substrate compared to the use of compositions containing compounds having low volatility, i.e., a boiling point of greater than 90° C. at atmospheric pressure or a vapor pressure greater than 70 mm of mercury at 25° C. It is an object of this invention to reduce the exposure level and the effective use level of the volatile components by adding adequate amount of pre-optimized solvent based compositions. It is further object of this invention to provide a composition which achieves enhanced and improved paint removal characteristics compared to prior art paint removal compositions.
2. Description of the Prior Art
The term “varnish and paint removal” as applied herein refers to chemical compositions which can strip or facilitate stripping of coatings, such as, paint, varnish, lacquer, shellac, polyurethane finishes and enamels, used to protect substrates such as wood and metal and to beautify them. Methylene chloride paint strippers are currently the industry standard for stripper performance. Methylene chloride strippers are effective for quickly softening most types of paints. The speed at which methylene chloride performs is believed to be due to its high solvent power coupled with high volatility as reflected by its extremely fast evaporation rate. This high volatility shortens the work life of methylene chloride paint strippers. Frequently, when methylene chloride paint strippers are used on thick accumulations of paint, more than one application is required since the work life is insufficient to permit penetration through the accumulation of paint. Methylene chloride is a chlorinated solvent which is closely regulated for environmental protection. Recently, it was discovered that methylene chloride can cause tumors in rats and mice. Since that discovery, the wide use of that solvent by industry and consumers has come under close scrutiny by federal regulatory agencies. N-methyl-2-pyrrolidone (NMP) has been employed in place of methylene chloride as the active ingredient in paint stripper compositions. Nelson, in U.S. Pat. No. 4,759,510, (Incorporated herein by reference in its entirety) for example, described a composition for this use having low volatility which included about 20% to 90% by weight of NMP and 30% to 70% by weight of an aromatic hydrocarbon solvent.
Mixtures of NMP and gamma-butyrolactone (BLO) also have been used as liquid formulations for removing screen printing inks. Madsen, in U.S. Pat. No. 4,836,950 (Incorporated herein by reference in its entirety), for example, described a liquid composition which included 1-25% by volume of NMP and/or BLO. Valasek, similarly, in U.S. Pat. No. 4,664,721 (Incorporated herein by reference in its entirety), described a composition which included 30-85% by weight of NMP and 10-35% by weight of an oxygenated solvent selected from esters and ethers. BLO was mentioned as a suitable component (lactone), although butoxyethanol and cyclohexanone were preferred. Caster, in U.S. Pat. No. 4,865,758 (Incorporated herein by reference in its entirety) described a method of removing paint with a lower alkyl substituted 2-oxazolidinone. In comparative results reported therein, it was disclosed that ethyl 3-ethoxypropionate had no effect on paint removal. McCullins, in British 1,487,737, described a paint remover composition for aerosol type paints in the form of a gel which included methyl ethyl ketone, ethyl acetate, ethoxyethanol and 2-ethoxyethyl acetate. This mixture of solvents was considered effective for paint sprayed graffiti as a viscous, transparent gel containing particles of silica or alumina in suspension. Palmer, in U.S. Pat. No. 4,120,810, (Incorporated herein by reference in its entirety) described paint remover compositions of NMP and/or BLO, and at least 35 mole % of blends of alkyl naphthalenes and alkyl benzenes.                These and other compositions, however, have not proven particularly effective for removing paint and varnish from wood and metal surfaces, without containing objectionable halogenated or aromatic compounds. Furthermore, they do not possess the attributes of being biodegradable, non-flammable, having a low vapor pressure and low toxicity.        Narayanan et al in U.S. Pat. No. 5,098,592 (Incorporated herein by reference in its entirety) (World patent No 5217640) have shown that a synergistic combination of NMP, BLO and ethyl 3-ethoxypropionate (EEP) is a very effective for removing varnish and several type of paints from wood and metal substrates. In Narayanan et al in U.S. Pat. No. 5,154,848 (Incorporated herein by reference in its entirety), a method is provided for removing or stripping varnish and paint from surfaces such a wood or metal which comprises applying a composition composed of NMP and/or BLO with about 1-30% by weight of an activator compound which is ethyl 3-ethoxypropionate (EEP) to the surface.        Fusiak in U.S. Pat. No. 5,334,331 (Incorporated herein by reference in its entirety) describes compositions of NMP/BLO and combinations activated by cyclomethacone at around 5% to remove organic coatings from substrates.        Fusiak et al in U.S. Pat. No. 5,049,300 (Incorporated herein by reference in its entirety) describes activation of NMP and combinations with acids        Known art of solvent based compositions for removal of paint, varnish coatings are non-aqueous, essentially free from water.        Several water based cleaning and spray compositions use powerful wetting agents and spreading agents. See: Robert Login et al on NOP use in multipurpose applications described in, WP 88/00184, U.S. Pat. No. 5,294,644 (Incorporated herein by reference in its entirety) and U.S Pat. No. 5,093,031 (Incorporated herein by reference in its entirety). Narayanan et al on synergy between NOP and Silwett L 77 (ethoxylated silicone) described in U.S. Pat. No. 5,508,249 (Incorporated herein by reference in its entirety), Rosen et al synergy between NOP and Alcohol ethoxylate, in U.S. Pat. No. 7,264,885 (Incorporated herein by reference in its entirety) and Narayanan et al (water dilutable NOP, alcohol ethoxylate synergistic composition, Easy wet 20) in U.S. Pat. No. 6,967,190 which is incorporated herein by reference in its entirety. See also Machac, Jr. et al, U.S. Pat. No. 6,159,915, incorporated herein by reference which describe paint removal compositions which describe as essential components, a carbonate, a dibasic ester and a monoester.        